An introduction to the Nuke Particle System

Using Nuke’s Particle System to speed up artist workflows

Once you’ve got to grips with it, the Particle System in NukeX has a set of use-cases and corresponding benefits that can make it a valuable tool to have in your compositing armoury.

Need to knock up a blood spurt from a gunshot wound, or the splash of raindrops on a pond? You can quickly and easily generate these kind of effects, right then and there in Nuke.

If you're not sure how to start, particle example toolsets have been included in Nuke 11 with setups for effects like snow and fog, each with their own tutorials to get you started (more on that at the end of this article).

The use of particle work inside of Nuke is growing, so it's well worth learning how to make the best use of particles across your shots to stand out as a compositing artist who can offer solutions right up to a deadline.

Some of the biggest studios in the industry already use the Particle System to get a significant speed advantage in their workflows.

With decisions increasingly being pushed into comp, using Nuke’s Particle System enables you to wait until you know what’s required before you invest time into specific elements of a shot: great when there's no time to go back to the FX department and get a new particle render for a non-hero effect.

In this article, we take a look at the Nuke Particle System and explain how to get the most out of it.

What is the Nuke Particle System?

Particle systems are environments which spawn and then track specific points (particles).

A particle is a dot or a point that exists in the 3D coordinate system. This point has certain attributes attached to it: typically they include things like how long the particle has been alive, what size it might be, and what it’s position and trajectory is.

You can include attributes specific to the type of particle simulation you’re running, like temperature (if you were doing an explosion), or viscosity (if you were doing a water splash).

The particle system tracks all of the particle information over a set time period and displays that in a way that’s interesting.

You can also do things like attach a piece of geometry to your particle, or a sprite, which is a 2D image that always faces the camera.

For example, you might want to create an explosion: it starts off with a point in space and you spawn a bunch of particles which burst very rapidly outwards.

You attach lifespan information, color information, temperature, and then for each particle in that system, you pull that data and derive what the particle will look like.

For a look at the Nuke Particle System in action, check out this video between 14:13 - 17:00, in which Ari Rubenstein gives an overview of how he used the system to create flotsam in his animated short, The Blues Crab.

How does Nuke’s Particle System help compositors?

Having a particle system within Nuke is great for compositors, because it means artists can more easily setup particle systems that match the plate they’re working with - whether that’s in the placement and alignment of particles, or in the interactions with card projection setups and geometry in Nuke’s 3D environment.

Similarly, if you’ve added additional information - like light information with Nuke’s Relight node - you can have the Particle System influenced by these additional comp elements.

As well as harnessing the power of Nuke’s nodes to influence particles’ look or behavior, all of Nuke’s tools are available for setting up the Particle System. Artists can use those tools to set up textures and pull data from the shot they’re working on to feed into the system.

This is really powerful, as it means artists can drive the Particle System using image information from their comp - giving potentially better integrated results and, when working in Nuke, a faster turnaround on seeing those results. This is particularly true after the speed improvements made to the Particle System in Nuke 11.3.

The ability to use the Scanline Render node and get additional data passes quickly - like normals, motion vectors, surface data and point data - without having to go to another application is also great for flexible workflows, and for doing more yourself as a comp artist.

Creating particle simulations and compositing at the same time means you can set up a scene quickly, look at the context, perform comp work, and then tweak the simulation based on what you’re seeing. You can then get immediate feedback, for a fast iteration loop.

In contrast, an effects artist will only look at the slap comp they’re provided for contextual information - which may not be properly graded or the latest version - and which therefore may not provide the best context.

All this means that rather than going to generate your particles in completely different software, you can quickly create something in Nuke and be ready and raring to go right then.

With just a little bit of knowledge of the Particle System, or a little bit of help from the particle toolsets included in Nuke, you can generate final-touch details - like puffs of dust from footfall on a dusty floor, for example.

It means that for the compositor, if they need to add an extra bit of detail to the comp, they don’t need to rely on another artist to generate that somewhere else and render it out for them: they can do it in Nuke. And that makes their workflow much faster.

What’s more, because Nuke is so customizable, you have the option to use Python and the API to really extend the Particle System if you chose.

What can the Particle System be used for?

Aside from the obvious use cases like rain and snow, there are a number of other useful applications of the Particle System.

It can be used for impact hits: to create spark hits for laser blasts or gunfire. It’s quick and easy to generate sparks that burst out from a specific point.

Similarly, it can be used for the embers in fire, cold breath, or dust motes.

If you’re attaching it to 3D geometry, you can bring in your 3D asset or character and position your omiters so they match the footsteps.

This is an easy way of achieving a realistic look efficiently, without having to go back to your 3D department.

It can also be used in conjunction with Nuke’s unique deep compositing capabilities to create some powerful workflows.

You can output deep compositing data for particles generated inside of Nuke, so you can have accurate holdouts without the need for re-rendering when other assets change.

Create some sheets of rain or a fog volume, and when you render using Nuke’s ScanlineRender node, you’ll have deep data for your particle effects.

You can then easily integrate and composite your particles with other deep data elements without having to render for holdouts, even if animation or models change later on. This creates a really dynamic and efficient workflow when working with assets that are likely to change - perfect in productions where updates are being made right up to the deadline, and not having to sim new particles with each change can drastically save you time.

For an introduction to deep compositing, check out Product Specialist Chris Wetherly’s presentation from SIGGRAPH 2018:

In it, Chris highlights some workflows that enable you to generate deep data out of Nuke’s 3D system, using just the in-built nodes.

This avoids a system performance hit or memory performance hit, because you’re generating inside of Nuke. These workflows can also be applied to the Particle System.

Why now is the time to explore the Particle System

There has never been a better time to explore Nuke’s Particle System.

With more and more work being pushed to later stages in production and into the compositing space, it’s more important than ever for compositors to know how they can make best use of all the workflows available to them in Nuke, and find solutions without having to go back in the pipeline.

For the most complex particle work like large scale hero effects and fluid simulations, there will always be a need for dedicated particle tools like Houdini.

But as decisions are increasingly pushed to comp, having a true particle simulation in Nuke allows you to defer more decisions until you know exactly what you need to achieve, and to quickly look dev work in a comp context, even producing the final results directly from your compositing application.

In the Nuke 11.3 release, significant updates were made to the Particle System. It can now produce up to 6x faster particle simulations and 4x faster playback of particles in the viewer.

In our tests, improvements are seen at any scale, with more improvement in simulations with a higher number of particles.

Watch the video below to see the difference in speed between Nuke 11.2 and 11.3.

As mentioned previously, for those unfamiliar with the Particle System, Nuke 11.3 also has common examples like snow and rain in-built, which you can load up and use as a starting point to learn from.

To access these toolsets, simply launch Nuke, hit tab and search for 'P_' to see the particle toolsets. Or alternatively, look for the dual spanner icon on the left toolbar to find the toolsets menu and go to the 3D subset.